Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B40/00—Preventing adhesion between glass and glass or between glass and the means used to shape it, hold it or support it
  • C03B40/005—Fabrics, felts or loose covers
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/02—Re-forming glass sheets
  • C03B23/023—Re-forming glass sheets by bending
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04B—KNITTING
  • D04B1/00—Weft knitting processes for the production of fabrics or articles not dependent on the use of particular machines; Fabrics or articles defined by such processes
  • D04B1/14—Other fabrics or articles characterised primarily by the use of particular thread materials
  • D04B1/16—Other fabrics or articles characterised primarily by the use of particular thread materials synthetic threads

Definitions

• the present invention relates to improvements in bending glass sheets by press bending heat-softened glass sheets into bent shapes, and particularly relates to an improved cover material for rigid shaping members which apply bending pressure to the opposite surfaces of heat-softened glass sheets.
• Glass sheets have been bent either by heat-softening one or more fiat glass sheets supported horizontally or obliquely over a suitable shaping surface until the glass conforms thereto by gravity sagging or by a method wherein the glass is heated to an elevated temperature and bending accelerated by applying pressure to one or both of the opposite major surfaces of each sheet by means of a pair of oppositely disposed, complementary shaped male and female pressing members.
• the pressing members act like forming dies that engage the opposite surfaces of the glass for a brief interval sulficient to shape the flat glass into its desired curvature. In this respect, the action is very much like that of a die-stamping operation.
• Such bending of glass has been termed press bending by the art.
• the glass press bending art has employed fiberglass cloth coverings to insulate the surface of the press members from direct contact with the heated glass.
• Prior to the present invention the art had suggested the use of a plurality of layers of Woven fiberglass cloth impregnated with a highly heat resisting plastic material filling the interstices of the woven fiberglass cloth.
• US. Patent No. 2,560,599 to Joseph D. Ryan shows this teaching.
• woven fiberglass cloth is susceptible of breakage due to the weak tensile strength of its fibers. It is necessary to stretch woven fiberglass cloth over the pressing members in order to minimize defects due to wrinkling of the cover. Intermittent contact of the fiberglass'cloth covers with glass sheets causes the glass fibers to stretch. Individual glass fibers break at only 3 percent elongation. Hence, frequent replacement of the impregnated woven fiberglass was required. This frequent replacement caused frequent interruptions in production.
• Such covers are susceptible of imparting a nonuniform pressure pattern to the heat-softened glass as the glass is pressed.
• a series of high pressure points located at each intersection of the warp threads and filling threads characterizes this pressure pattern.
• the imprint of the fiberglass fabric is especially noticeable in the bent glass at these high pressure points.
• Knit fabrics differ greatly from woven fabrics and nonwoven fabrics. Instead of having an interlacing of a series of lengthwise and crosswise threads as in woven fabrics or a series of webs or layers of fabric bonded together as in nonwoven fabrics, knitting, in its simplest form consists of forming loops of yarn and drawing other loops through those previously formed.
• the knitted fabric structure consists of a pattern of intersecting loops. When knitted covers are employed as faces for glass pressing dies as suggested by the present invention, the loops of the fabric contact the glass.
• Knitted fiberglass material can be made on either flat or circular knitting machines. All general types of knitted material, such as plain, ribbed, lockstitch and mesh or warp-knits, such as tricot and milanese, are vastly superior to woven fiberglass material for pressing mold covers. The reason for this superiority is that all knit fabrics have elasticity and recovery properties 'in all directions. These properties are absent from woven and nonwoven fabrics.
• the knitted fabrics preferred for use in the present invention consist throughout their structure of a multi- 7 plicity of loops and loop linkages that are bound to each other, ahead and behind, to the right and to the left.
• a normal loosely knit loop consists of two jointed s forms.
• linkages from loop to loop follow continuous 8 paths.
• Cross linkages other than of S shape lessen the elasticity of the fabric in proportion to their concentration.
• Knit fabrics are capable of stretching in any direction to a gretater extent than woven or nonwoven fabrics. Knit fabrics stretch by distorting the configuration 'of their loosely knit intersection loops. Hence, knit fabrics are more capable of conforming to the complex shapes of the shaping surfaces of complementary glass pressing members than woven or nonwoven fabrics.
• Loosely knit fiber glass cloth covers are draped over possible elasticity and recovery convex shaping surface.
• the cover secured to the frame attached to the concave shaping member conforms to the concave shaping surface when the hot glass is engaged due to the elasticity and recovery properties of the knit fiberglass cloth cover.
• Knit cloth with open loops is more resilient and has better recovery properties than woven or nonwoven cloth and conforms more precisely to the shaping surface than Woven or nonwoven cloth. This characteristic lessens the likelihood that the cover will wrinkle.
• Knit fiberglass cloth encloses a greater volume of dead air space than woven fiberglass cloth because of the looped configuration of knit fabrics.
• the air spaces provide improved thermal insulation compared to that provided by woven or nonwoven fiberglass cloth. Therefore,
• the texture of the yarn further improves the thermal insulation properties of the fiberglass cloth and further reduces the likelihood of imposing the overall pattern of the cover on the glass.
• Knit fiberglass cloth has a longer life expectancy than Woven fiberglass cloth, because the knit fiberglass cloth loops maintain their resiliency even after repeated contact with hot glass under conditions such that the individual fibers of woven or nonwoven cloths would elongate to their point of rupture.
• This resiliency of the loops maintains the knit fiber cloth in intimate contact with the adjacent surface of the pressing members at elevated temperatures.
• Woven fiber cloth does not have such resiliency and, therefore, tends to stretch out of intimate contact with the shaping surface of the pressing members, thereby inducing wrinkling of the fiberglass cloth. This wrinkling induces wrinkles in the viewing surfaces of the pressed glass and also accelerates rupture of the yarn.
• the shaping members were held in pressurized contact with the opposite surfaces of the glass sheet for about 2 seconds and then were retracted to receive a subsequent heat-softened glass sheet therebetween for shaping.
• the glass sheets were immediately transported from the press ing station to a quenching station where air blasts were directed against the opposite major surfaces to quench the glass and impart a temper thereto. After the glass sheets were chilled, they were inspected for surface markings.
• the glass shaping members were made of cast iron with various fiberglass cloth coverings, some knit and others woven, mounted in intimate contact with the complementary shaping surfaces thereof. Optical inspection of the bent glass provided a test for the various woven and knitted fiberglass cloths employed as covers for the glass pressing members.
• cover materials are listed in their order of preference with cover material I the best and cover material IV the worst of those listed.
• cover material I the best and cover material IV the worst of those listed.
• cover material IV the worst of those listed.
• the optical properties of bent glass sheets produced using cover materials 111 and IV did not meet present commercial requirements.
• the knitting pattern must not be either too loose or too tight. 7 If it is too loose, the spacing between adjacent loops causes the knit fabric to fail to provide a suitable uniform insulation. The hot glass surface is distorted as when using woven or nonwoven fiberglass covers having insufficient insulation uniformity.
• 150-1/ 2-3.8 S fiberglass yarn is suitable as a cover to minimize cloth marking of the pressed glass surfaces in a range of about 9 courses to about 30 courses.
• heavier gauge yarns are more loosely knit than lighter gauge yarns.
• a 30 gauge cloth (20 needles per inch) of this material works excellently when it is knit with about 20 to 30 courses per inch, and a 12 gauge cloth (8 needles per inch) preferably is knit with about 9 to 12 courses per inch.
• Fabrics of 6 needles per inch and less of this yarn are generally not suitable as covers because they mark heat-softened glass with their imprint.
• a larger number of courses is desirable for a finer yarn, such as 150-1/ 0-1.0 2. Suitable covers result when this finer yarn is knit into fabrics of from about 12 to about 36 courses.
• a suggested range for a 12 course fabric of this yarn is about 15 gauge minimum needles per inch) and up, whereas for a 36 course fabric of this fine yarn, a range of 20 to 30 gauge is suggested.
• the amount of insulation required for the convex shaping member is greater than that required for the concave shaping member.
• several layers of woven fiberglass cloth were required to furnish sufficient thermal insulation for each of the shaping members.
• Substitution of knit fiberglass cloth for the prior art woven fiberglass cloth has resulted in the need for fewer layers on the shaping surfaces of the shaping members.
• the glass sheet surface facing the convex shaping member is in contact with more area of the shaping surface than the glass sheet surface facing the concave shaping member for a considerable portion of the pressing cycle, more insulation is needed between the glass and the convex shaping member than between the glass and the concave shaping member.
• said complementary shaping surfaces are convex and concave, comprising interposing at least one more layer of knit fiber glass cloth between said convex shaping surface and one surface of the glass sheet than the number of layers of knit fiber glass cloth interposed between said concave shaping surface and the other surface of the glass sheet.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Textile Engineering (AREA)
• Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
• Laminated Bodies (AREA)
• Knitting Of Fabric (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22651917

Family Applications (1)

Country Status (7)

Cited By (22)

Families Citing this family (2)

Citations (1)

• 0
  • BE BE629375D patent/BE629375A/xx unknown
  • NL NL289868D patent/NL289868A/xx unknown
• 1962
  • 1962-03-08 US US178278A patent/US3148968A/en not_active Expired - Lifetime
• 1963
  • 1963-03-06 GB GB8902/63A patent/GB983805A/en not_active Expired
  • 1963-03-07 SE SE2496/63A patent/SE307633B/xx unknown
  • 1963-03-07 DE DE19631471933 patent/DE1471933B2/de active Pending
  • 1963-03-08 AT AT182563A patent/AT259152B/de active

Patent Citations (1)

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